Introduce subcall32.h and subcall64.h wrappers

Introduce subcall32.h and subcall64.h wrappers

They are going to be used to implement new parsers for indirect
time-related syscalls.

* linux/subcall32.h: New file.
* linux/subcall64.h: Likewise.
* Makefile.am (EXTRA_DIST): Add them.
* linux/arm/syscallent.h: Replace "subcall.h" with "subcall32.h".
* linux/i386/syscallent.h: Likewise.
* linux/m68k/syscallent.h: Likewise.
* linux/mips/syscallent-n32.h: Likewise.
* linux/mips/syscallent-o32.h: Likewise.
* linux/powerpc/syscallent.h: Likewise.
* linux/s390/syscallent.h: Likewise.
* linux/sh/syscallent.h: Likewise.
* linux/sparc/syscallent.h: Likewise.
* linux/mips/syscallent-n64.h: Replace "subcall.h" with "subcall64.h".
* linux/powerpc64/syscallent.h: Likewise.
* linux/s390x/syscallent.h: Likewise.
* linux/sh64/syscallent.h: Likewise.
* linux/sparc64/syscallent.h: Likewise.